1. Field of the Invention
This invention relates to sealed bearing rotary cone rock bits that utilize a belleville seal to keep detritus out of the bearings and lubricant within the bearing surfaces during rock bit operation.
More specifically, this invention relates to a belleville seal wherein the inner diameter of the encapsulated belleville spring is isolated from the proposed static seal by means of an intervening metallic ring, the ring being secured to a junction formed between a journal bearing and a leg backface.
2. Description of the Prior Art
Prior art belleville springs utilize one or two belleville springs encapsulated within a rubberlike compound. The inner diametric portion of the belleville seal consists of a metallic ring that overlaps the inner diameter of the belleville spring such that the inner diameter of belleville springs are severely constrained during installation of the seal onto the journal bearing.
An example of this type of belleville seal is found in U.S. Pat. No. 3,489,421, assigned to the same assignee as the present invention. The patent discloses an annular seal that is affixed to one of two relatively rotatable members for creating a seal therebetween. The inner perimeter of the seal comprises a metal retaining ring having an interference fit on one of the parts to be sealed. Extending generally radially outwardly from the metal ring is a spring element which may comprise two or more belleville springs which are held by and connected to the retaining ring by a rubberlike compound bonded to the springs and to the retaining ring. The inner diametric static portion of the spring is tightly fitted upon a hub or journal bearing forming an interference fit. The metal ring is then spot welded to the hub to prevent rotation of the seal on the static side of the seal. The dynamic part of the seal is, for example, located adjacent the outer peripheral diameter of the seal; the dynamic face being formed between the outer diameter of the seal and the rotary cutter cone mounted to the journal.
U.S. Pat. No. 3,680,873, also assigned to the same assignee as the present invention, discloses a belleville seal for use between relatively rotatable parts and includes an inner annular ring of metal and an integrated outer annular seal element of yieldable material. The metallic ring forms the static portion of the seal. The ring is resilient and has a weakened point formed therein. The ring remains unbroken during the seal fabrication process wherein the elastomer is molded to the ring. The ring is separable at the weakened breakpoint when forced over an annular abutment on one of the relatively rotatable parts. The inner metal ring attached to the rubberlike material returns approximately to its original diameter after passing over the abutment. The resilient material is subjected to pressure deformations to tightly secure the resilient ring radially inwardly about the relatively rotatable part and axially outwardly against the abutment. After the inner metallic ring is forced over the abutment, the ring is partially metallurgically bonded (spot welded) to the journal bearing to prevent rotation of the inner static portion of the seal during operation of the bit in a borehole.
Both the '421 and '873 patents disclose an inner metallic ring that is securely attached to the journal bearing on the static side. The ring forms an annular lip that overlaps the inner diameter of the encapsulated belleville spring or springs. When the belleville seals are installed during the assembly process, the oversized resilient material is pressed into the junction between the journal bearing and the leg backface. The annular flange or lip of the metallic rings then traps or compresses the inner diameter of the encapsulated belleville springs, thereby placing the springs in a preloaded condition. Hence, during operation of the belleville seal, the springs, as they are deformed, increase in load, i.e., for an installed seal the load continues to increase through its entire range of deflection in the foregoing prior art devices.
The present invention isolates the belleville spring encapsulated within the seal material such that as the inner metallic static portion of the seal is affixed to the journal bearing, the encapsulated belleville spring is free to function without constraint induced by the preload.